DE2937463A1 - GASKET FOR TURBINE ENGINE COVER - Google Patents

Description

Seal for turbine engine casing

The invention relates to gas turbine engines and, more particularly, to engines having a jacket that surrounds the tips of the
Surrounding rotor blades in the turbine section of the engine. In such a gas turbine engine, compressed air and
Fuel burned in a combustion chamber to add thermal energy to the gases flowing through it. That from the chamber
Exiting working fluids are gases of high temperature that flow downstream in an annular flow path through the turbine section of the engine. Guide vanes at the entrance to the turbine direct the gases at a plurality of vanes that protrude radially outward from the engine rotor. A
an annular jacket carried by the engine casing surrounds the tips of the rotor blades to contain the gases flowing therethrough to the flow path. The clearance between the blade tips and the jacket is made as small as possible in order to prevent the gases from leaking around the blade tips.

A limiting factor in many engine designs is
the maximum temperature of the gases which can be permitted in the turbine without the service life of the individual components being adversely affected. The coats that are the tops of the
Surrounding rotor blades are particularly sensitive to thermal damage. Because of the tight margins between the
In addition, because of the various stresses to which the engine components are exposed, the blade tips easily rub against the sealing surface of the shell segment. Thus, the jacket material must be easy to grind so that it does not damage the blade tips and
not excessively abraded by any limited contact. The aim of the present invention is to provide such a jacket material for a gas turbine engine.

0300U / 0733

It has now been found that a sealing surface for use in a gas turbine engine casing for aircraft engines and the like can be made with both excellent high temperature and abrasive properties can. The sealing surface opposite the blade tips the jacket is made of an amphoteric, highly heat-resistant oxide matrix, a phosphate binder and optionally a stabilizer, reinforcement and / or porosity control agent.

The phosphate suitable for bonding the jacket matrix materials according to the invention should be at the engine temperatures used or be stable at temperatures above about 135O ° C. Examples of suitable phosphates are aluminum phosphate (AlPO ^) and zirconium pyrophosphate (Zr "P" 0). It can Mixtures of phosphates can also be used, and likewise phosphoric acid (H, PO ^), since it is a stable phosphate during the reaction forms.

Amphoteric refractory oxides that can be used as matrix materials are those that are stable at the required high temperatures, and preferably they have a coefficient of thermal expansion similar to that of the superalloy metallic cladding block and also low thermal conductivity to provide less cooling require. Furthermore, they are preferably stable in both oxidizing and reducing environments. Examples of suitable materials are aluminum oxide (Al 0), cerium oxide (CeO ₂ ), thorium oxide (ThO), stabilized hafnium oxide (HfOp) and stabilized zirconium oxide (ZrO _? ). Stabilized zirconia is preferred because its coefficient of thermal expansion is closest to the high temperature aircraft metals currently used and it has low thermal conductivity so that it requires less cooling than other materials. The ratio of the amphoteric oxide to the binder can be in the range of about 8: 1 to 2: 1.

0300U / 0733

Stabilizers that can be used are those which are stable at the engine temperatures used or at temperatures above about 1350 ^° C. and which prevent a monoclinic into tetragonal transformation in zirconium oxide or hafnium oxide. Such stabilizers include yttrium oxide (Y "0) magnesium oxide (MgO) and calcium oxide (CaO) or a rare earth oxide. Typical rare earth oxides are: erbium oxide, europium oxide, scandiura oxide and ytterbium oxide. Ytterbium oxide is preferred especially in connection with zirconium oxide or hafnium oxide. The amount of stabilizer used will depend on the particular stabilizer, the matrix material and other variables, but in general a lot of 4 to 50 wt -.% Of the matrix material be sufficient. Solid fillers for controlling the reinforcement or porosity of the material include a variety of materials, which are preferably included but not always required. For example, materials such as graphite are burned at the high temperatures encountered in turbine engines, but they are useful in controlling the porosity and subsequent hardness of the associated amphoteric refractory oxide. Other materials like sawdust or plastic filler serve the same purpose. Reinforcing materials that do not burn out at the elevated temperatures that occur include silicon carbide fibers (whiskers), which serve to improve the fracture toughness and thermal shock resistance of the composition. Other materials that can be used are fibrous high-temperature oxides such as aluminum oxide or zirconium oxide. Reinforcing materials, such as silicon carbide fibers, preferably have a length between about 3 to 10 mm, a thickness of about 0.04 to 0.1 mm and a width of 0.1 to 0.5 mm.

The particle sizes for the amphoteric high temperature resistant oxide matrix materials preferably range from about Submicron range down to 40 microns (micromillimeters) in order for a more complete reaction, although larger particles up to 100 microns can be used as fillers.

0300U / 0733

The materials are made by adding the amphoteric high refractory oxide, the phosphate-containing material, and an amount of pesticide filler material between about 0 and about 2 % by weight. that provide the desired porosity and abrasive properties, and enough distilled water is added to form a pourable paste that can be poured. The paste is heated between about 4 and about 48 hours at a relatively low temperature of between about 80 and about 120 C until it is dried to the paste to set, and then it is at an intermediate temperature between about 12O ¹ "and about l60 ° C cured for about 1 to 24 hours to remove most of the free water, and then it is finally cured at an elevated temperature between about 500 and IQQQ ⁰ C for about 1 to 2M hours to remove all of the chemically bound water so that the cement cannot be loosened again,

Using common molds and materials, this can be done The resulting material can be poured and cemented in a conventional metallic mantle block to form a sealing surface and to form a sheath material that is easy to grind.

The following examples serve to explain the invention in more detail and preferred embodiments. All parts and percentages in the examples and elsewhere in the Description and claims are by weight? Unless otherwise stated.

example 1

In a crucible made of plastic, 20 g of zirconium oxide with the size of the particles that fell through a sieve with a mesh size of 0.045 mm {-325 mesh), stabilized with 12 % Yp ⁰ ^ {Zireonium Corporation of America), 5 g zirconia with a submicron particle size {Zircar Products Inc.) and 3.75 g of ^ SiC whiskers added. The materials were mixed intensively to form a nearly homogeneous dry mix. This mixture was 8 g of

030Ö14 / 0733

85% H PO ^ and up to 2 g of distilled water are added to form a pourable paste that can be poured into a 4.91 x 2.45 x 0.58 cm mold. The paste was heated at 100 ° C for 4 hours in an electric muffle furnace until the paste was set to become free-standing. It was further heated at 150 ⁰ C for an additional two hours until it was dry and further cured at 600 ° C for 4 hours. The material had a surface Rockwell hardness of 93 using a 12.5 mm (1/2 inch) steel test ball and a load of 15 kg. Grinding tests showed that the material is easy to grind. The material had an open porosity of about 30 %.

A test specimen was then cut from the rod with a diamond wheel and the integrity of the specimen was maintained when repeated to near incandescent in one Heated the oxygen-methane flame and immediately put it in cold water was immersed. Thus, the material had excellent thermal shock resistance.

Example 2

In a plastic container, 20 g of zirconia having a particle size that passed through a sieve with a mesh size of 0.045 mm (-325 mesh) stabilized with 12 % YpO, ^and 3 E ^ -SiC whiskers were placed. The material was mixed intensively dry and 10 g of solution were added to this mixture. The material was poured into a PO ^)

form with the dimensions 5.32 χ 2.53 x 0.63 cm, which was ^{heated for 12 hours at 80 0} C, 2 hours at 100 ° C and 2 hours at 120 ⁰ C until it had completely tightened or was standing. Additional heating for 2 hours at 200 ^° C. and 6 hours at 600 ^° C. completed the heat treatment. The cured material had a density of 2.74 g / cm3 and good solid-state erosion resistance.

030014/0793

Examples 3 ~ 5

In a crucible made of plastic, 20 g of oxide or hydroxide of thorium, hafnium or cerium with the size of the particles that fell through a sieve with a mesh size of 0.0 ^ 5 mm (-325 mesh), and 3 g » x SiC whiskers. The materials were intensively dry mixed to form a homogeneous mixture, and 8 g of phosphoric acid or 10 g of A1 (H "PO.)" Was added to this mixture. The materials were further mixed to form a paste or pourable mixture and poured into the desired shape or shroud block for the engine turbine. A heat treatment of H - 25 hours at a temperature of 80 - 120 ⁰ C caused a setting or a setting ^ and a further gradual heating to 600 ⁰ C caused a final hardening. The final materials had essentially the same properties as. the materials described in Examples 1 and 2, but the coefficients of thermal expansion are similar to the coefficient of expansion of the high- temperature resistant oxide used.

030014/0733

Claims (6)

Expectations Iy seal for a gas turbine engine with several arc-shaped segments arranged at their ends adjacent to one another, which surround the tips of the rotor blades of the engine, each segment having a sealing surface opposite the blade tips, characterized in that the sealing surface consists of (a) an amphoteric high-temperature-resistant oxide matrix of ZrO, Al "0, Ce ₃ O, ThO ₂ , HfOp or mixtures thereof, (b) a phosphate binder that is stable above 135O ° C, the weight ratio of the oxide matrix to the phosphate binder being in the range of 2: 1 to 8: 1 , and optionally (c) up to 50 % (based on the weight of the matrix material) of a stabilizer selected from YpO. ,, MgO, CaO, rare earth oxides, or mixtures thereof, and (d) up to 25 % ( based on the weight of the matrix material) is formed from a filler. 2. Seal according to claim 1, characterized in that the amphoteric high temperature resistant oxide ZrO is. 0300U / n7 * 3 3. Seal according to claim 2, characterized in that 4 to 50 % ^ ₂ O is used ^{as e} ^ ⁿ stabilizer. ¹ J. Seal according to claim 1, characterized in that a mixture of Η-, ΡΟ ^ and AIPO ^ is used as the phosphate. 5. Seal according to claim 1, characterized in that graphite, silicon carbide fibers as a filler or a mixture thereof is used. 6. Seal according to claim 1, characterized in that the sealing surface stabilizes ZrOp with Υ, -, 0. ,, H, to ,, and silicon carbide fibers. 0300U / 0733